Background to the exercise
IEA Wind Task 32 Workshop 14 will focus on the use of nacelle mounted lidars for wind turbine power curve verification (PCV) in complex terrain.
A new standard (IEC 61400-50-3) for wind measurement using nacelle-mounted lidars is currently under development. This standard will describe the prescribed calibration procedure , the sources of uncertainty to be accounted for and the measurement methodology highlighting specific requirements for nacelle mounted lidars. However, the scope of this standard is limited to applications in flat terrain or offshore.
We therefore propose to build evidence of application in complex terrain based on actual measurement campaigns, leading to a Task 32 workshop on the theme (Workshop 14). The objective of WS14 is to present and discuss possible ways of using nacelle mounted lidars to fulfill the needs for a practical and reliable method for PCV in complex terrain. The primary objective is to prepare a proposal for an addendum to IEC 61400-50-3 to extend the scope to moderately complex terrain - a short term solution - including actual practice of the method or part of it. The secondary objective is to discuss all possible methods and their challenges/needs for further development, which would lead to a long term solution.
In preparation to the workshop and to ensure a high-level discussion, we invite owners of complex terrain nacelle lidar datasets to participate in an exercise to evaluate 2 methods.
Method 1: site calibration and power curve measurement using a nacelle lidar. This method follows requirements from the IEC 61400-12-1: 2005 as close as possible while replacing the met mast with a nacelle lidar. The wind speed is measured at hub height at 2.5D upstream of the rotor. A detailed guideline is given in Annex A in the summary document on this page. Additional modifications to the method are welcome but results should include strict application of Annex A in addition to any modified approach so that results can be compared.
Method 2: the wind speed is reconstructed from the LOS speed measured by the nacelle lidar at 3 or 4 distances between 0.5D and 1D upstream of the rotor and using a simple induction model (no site calibration). This is similar to the approach developed and tested in the UniTTe project (see Wagner R et al., WESC2019) and discussed in IEA Task 32 WS11 (see Nygaard NG, WESC 2019).
Who should participate in the exercise?
We therefore invite anyone who is planning or currently running a measurement campaign using a nacelle mounted lidar to either try out one or both methods on her/his own dataset.
In this exercise, each participant works on his/her own dataset. Only normalized results will be shared. The group provides and discusses the methods. The results will first be discussed amongst the exercise participants through several video conference calls. The lessons learned will then be presented and discussed within a broader audience in Workshop 14 in 2020. Participants in the workshop will be have the opportunity to present their results and learnings. The workshop learnings and conclusions are expected to be published or presented at a conference and form the basis for a proposal to PT 61400-50-3.
What you need to take part in the comparative exercise
You can take part in the comparative exercise if you have a dataset or expect to have one by February 2020.
The minimum data needed to participate to the exercise are:
- Power curve measurement using a nacelle lidar in moderately complex terrain.
- Site calibration.
- An independent wind speed measurement (e.g. met mast or ground based lidar) is recommended.
More details are provided in the attached document.